CPU: Intel Core i5-3570K 3.4GHz Quad-Core Processor ($219.99 @ Amazon)
CPU Cooler: Cooler Master Hyper 212 Plus 76.8 CFM Sleeve Bearing CPU Cooler ($26.98 @ Amazon)
Motherboard: ASRock Z77 Extreme4 ATX LGA1155 Motherboard ($134.99 @ Amazon)
Memory: Corsair Vengeance 8GB (2 x 4GB) DDR3-1600 Memory ($61.26 @ Amazon)
Storage: Western Digital Caviar Green 2TB 3.5" Internal Hard Drive - Already Own
Video Card: Gigabyte AMD Radeon HD 7970 OC Video Card (1000Mhz Core Clock) ($399.99 @ Amazon)
Case: Xigmatek MIDGARD II (Black) ATX Mid Tower Case ($74.99 @ Amazon)
Power Supply: Corsair Enthusiast 650W 80 PLUS Bronze Certified ATX12V / EPS12V Power Supply ($89.99 @ Amazon)
Optical Drive: Asus DRW-24B1ST/BLK/B/AS DVD/CD Writer ($19.96 @ Amazon)
Monitor: Asus VE228H 21.5" Monitor ($134.99 @ Amazon)
OS: Windows 8 Pro Full with Windows Media Center - Already Own
Mouse: CM Storm Spawn - Own
Gaming Keypad: Razer Nostromo - Own
Keyboard - Any generic KB I can find
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-03-14 22:01 EDT-0400)
1. The power supply
2 .Caviar greens shouldn't be used for the operating system
Personally I think you should get a better power supply, but I think your fine with that one.
The green drives are meant for storage, not running an operating system; a 120GB SSD would be a good choice.
I think the Hyper 212 is fine unless you want to go beyond 4.0ghz.